Automatic electric fusion welding apparatus and process



Feb- 8, 1949- J. A. KRA-rz ET AL AUTOMATIC ELECTRIC FUSION WELDINGAPPARATUS AND PROCESS Filed Feb. 5, 194s Tobozou Tw.

JOMFZOO f BY miv iw-JLL ATTORNEY atented Feb. 8, 1949 AUTOMATIC ELECTRICFUSION WELDING APPARATUS AND PROCESS VJohn A. Kratz, Yonkers, N. Y., andHenry G. Thoma, Rutherford, N. J., assignors to The Linde Air ProductsCompany, a corporation of Ohio Application February 5, 194.6, Serial No.645,648

(Cl. 21B-8) 9 Claims.

This invention relates to electric fusion welding ind more particularlyan adjustable automatic welding system.

lin the use of submerged melt welding for rivet or plug welding or shortseam welding, a troublesome problem is involved due to the presence ofthe special granulated material which is non-J conductive when cold.Such material fills the space between the wort: and the electrode orWelding rod, so that automatic starting cannot be accomplishedconsistently by having the electrode touch the work and then withdraw toestablish the arc. 'Nor is it feasible, in view of time element,manually to clean such granu= lated material from the space between theelcc1 trode and the Work, and insert a starting fuse, at the beginningof each weld in intermittent `welding, in order to start each weld. .cuiobject of the invention is to solve such problem.

Such problem is solved according to the in vention by novel automaticmeans for discharging a high-frequency potential through the mediumbetween the electrode and Worlr for a short time only prior to the startof each weld. Advantages vresult in that the high-frequency generator isactive only during a small fraction of the welding cycle, greatlyincreasing the life of such geng1 erator, and considerably reducing thetime of possible interference due to the high-frequency output thereof.

Another important object of the invention is to provide improved meansto prevent damage to the welding machine and circuit elements andcomponents associated with the system due to the high frequency, evenduring the short time that the high-frequency generator is in operation.

The primary purpose of the invention isfto provide an entirely automaticelectric fusion welding system for generating and applying ahigh-frequency potential between the Work and welding electrode whileslowly feeding such electrode toward the work, discontinuing thegenerathe high-frequency potential generation.

The single figure of drawing is a diagram of a circuit for use in theinvention.

Referring to the drawing, a welding head H is provided in which a metalwelding electrode $15,. such as a length of Wire or rod, is arranged tobe fed through an electrical jaw contact i2 by a rod feed roll i4. Theroll i4 is driven by a rod feed motor it comprising an armature it and aseparately excited field winding 2li. The electrode iii is fed towardanother electrode such as the work 22 to be welded, by the motor iii ata rate such that the normal welding voltage between the electrode andthe Werl: is kept sub-z stantially constant by means oi an automaticwelding voltage control itt, such as that disclosed by Patent 2,266,5i0.

The input circuit of the welding voltage conm trol includes leads ttland connected to the contact it and work 22, respectively. Lcad 26 isconnected to one side of a high-frequency choke coil or reactance il theother side of which is connected to a grounded conductor 3l! through ahigh-frequency icy-pass condenser 32. The condenser and choke arecontained in a highfreoucncy filter unit B. The latter side of the chokecoil is also connected by a conductor 3E to one terminal of an "inchingswitch 3S in a switch box S, the opposite terminal of switch 3B beingconnected by a conductor 3B to a. doublepole double-throw reversingswitch I0 in a. timing and control unit A, thence to the voltage con1trol 24 by conductor 42.

The other lead 28 is connected to conductors 44 and 46 leading to theinput circuit 48 ci' a welding voltage-responsive relay 50, and thenormally closed output circuit t2 of a Welding time-delay relay Eil. Theinput circuit Q8 of relay til is connected by a conductor 5G to one sideof a resistor E58 provided with a shunt switch B0. The switch El) isclosed when welding with alternating current, and opened when Weldingwith direct current. The other side of the resistor 58 is connected byconductor 62 to the electrode lead S6 of the welding circuit. The outputcircuit of relay 50 includes a Single-pole double-throw contactor 86which closes the output circuit at an applied maximum voltage, forexample, of about 7o volts, to the input circuit 48; and opens when theapplied voltage drops below a minimum value, ior example, of about 60volts. Thus, the relay to is responsive to the voltage between the work22 and electrode l0, automatically opening its output circuit when .thewelding circuit is open, and closing such output circuit when thewelding circuit is closed.

The output circuit of relay 5U includes, in addition to contacter 66, aconductor 10, switch 12, a conductor H, input circuit 16 of timedelayrelay 64, conductor 18 and a normally closed 84' and 86; respectively.Thus, when the contactors 66 and 80 are closed, the time-delay relay E4is energized. Since such relay controls the welding interval when it isenergized, it may be called the weldi-ng time-delay relay. The inputcircuit 'i6 of the relay 54 may be shunted around the contacter 66 ofthe relay 50, by moving the switch l2 from circuit relation withconductor 28 and into circuit relation with conductor 86. By opening theswitch l2, the input circuit i6 of the relay 50 may be disconnected fromboth of the conductors l@ and 86. Normally, however, the switch l2 isclosed in circuit relation with the conductor 86.

The output circuit of the welding time-delay relay 58 includes, inaddition to the normally closed contactor 52, a conductor 88, switch 88and conductor of the welding voltage input circuit of the automaticvoltage control 28. When the contactor 52 is open, the input controlvoltage is zero, so that no rod-feed takes place.

The output circuit of the relay |58 also includes a conductor |02, theinput circuit |04 of a nonwelding time-delay relay |06, and conductor|08 which is connected to the power supply lead 90. Thus, when thecontactor 66 closes, the relay |06 is energized, closing a normally opencontactor ||0 in series with conductor |02, and the input circuit ||2 ofrelay 82 by way of conductor H8, at the end of apredetermined timeinterval, which is adjustable. When the contactor ||0 closes, the relay82 is energized by the power supply circuitld, opening its contactor 80,deenergizing the input circuit i6 of relay 54.

The contactor 80 is also in control circuit relation with a carriagedriving motor ||6 by way of the conductor 18, conductor H8, and, aseries switch |20, the other terminal of the motor being connected tothe power supply lead 88. Thus, opening of contactor 80, deenergizesmotor 2|6, when the switch I 20 is closed. The motor IIS is connected todrive the work 22 or the welding electrode I0 in the direction of thewelding seam during a seam welding operation. For example,

the rod feed motor I6 and the contact I2 may be'mounted on a suitablecarriage which is driven by the motor ||6 with respect to the work 22along a desired path. Or, the motor |I6 may drive the work 22 withrespect to a stationary Welding head on which the contact I2 and.rodfeed motor are mounted.

In addition to the normally closed contactor 80, the relay 82 isprovided with another normally closed contactor ||8 in shunt circuitrelation with an adjustable' resistor |20, the latter being in serieswith the output circuit of the voltage control 28 which includes thearmature I8 of the rod-feed motor I6. Thus, the opening of contactor I|8, causes the resistor |20 to function in such circuit to reduce thespeed of the armature I8, and hence that of the rod feed. The circuitinvolved includes conductors |22, |24 from the voltage control 24,conductors |26, |28, a reversing switch |30, conductors |32, |34,highfrequency choke coils |36, |30, and armature leads |40, |42.High-frequency by-pass condensers 44,.

|46 are provided between the conductors |32, |34 and the groundconnection 30.

The relay 82 is also provided with a normally open contactor |08 in thepower supply circuit of a high-frequency generator |50, which circuitincludes conductor |62, primary winding |54 of a transformer |66, aseries switch |58, conductor |609. substantially constant-voltage powersupply circuit iBZ, and conductor |64. Thus, powc'r is supplied to thegenerator |66 only when the contactor |88 and switch |58 are closed.

The high-frequency generator |60 also comprises a high-voltage secondarywinding |66 of the transformer |56, connected to spaced electrodes |68of a spark-gap, and to a circuit including an inductance |76 and acapacitance |12, tuned to provide a high-frequency generating outputwhen the transformer |56 is energized. The inductance il@ is coupled toan air-core coil |78 in the welding circuit lead 64|, so that thehighfrequency output of the generator |50 is applied to the medium il@between the work 22 and Welding rod i0 before the latter touches suchwork. vift high-frequency by-pass condenser |18 is connected between theWelding lead 04, and

a welding lead |80 which is connected to the work 22.

The leads 58 and |80 are supplied with welding current by a weldingtransformer or generator |82 which is adapted to be connected to thepower supply circuit |62 by suitable circuit means including a normallyopen contacter |80 which is remotely controlled by a contactor switch|08. When the switch is closed, the control circuit of contactor |865 isenergized by the supply circuit 86| through conductor 80,` conductor 88,conductor 86, conductor |88, switch |86, conductor |90, contacter |84',conductor |92, conductor 90, and conductor 96.

The voltage control 28 is provided with an output circuit includingconductors |84, |86 which are connected to the rod-feed motor winding 20through high-frequency choke coils |97, |98. The terminals of the latteraway from the winding 20 are grounded through high-frequency by-passcondensers 200, 202, and conductor 30.

The medium |76 is a granulated composition which is a non-conductor ofthe welding current when cold. Therefore, in starting the welding actionmeans is provided to conduct the welding current through such mediumbetween the end of the rod I0 and the work 22 to start the weldingaction. If the rod i0 is allowed to touch the work 22, such contact maysometimes cause a' small amount of metal to fuse and freeze the rod tothe plate, resulting in an undesirable short circuit.

Prior to the invention, the usual method of starting the weld was toplace a small wad of steel wool between the end of the rod and the work.The steel wool, being a ccnductor, carried the welding current just longenough to establish conditions for starting the weld; it then melted andbecame part of the weld. Such method was satisfactory where the timeconsumed in placing the'ball of steel Wool was short in comparison tothe time of welding. However, in cases such as plug welding,intermittent welding,

or production-line welding where there are nution consists of three mainparts: the timing and starting control A, the high-frequency filteringunit B, and the high-voltage, high-frequency generating unit C. Thehigh-frequency generating unit C contains the stepup transformer |44,spark gap, and condenser |12, which develop a high-potential radiofrequency output. The unit C is connected in series with the mainwelding current cables 64, |80 so placed that one side of thehigh-frequency potential circuit is connected to the electrode I and theother side to the ground through the by-pass condenser |14. Suiflcientvoltage is produced to cause a spark to jump a certain distance such asa 11e-in. gap between the electrode l0 and ground. The spark is notaiected by the welding composition |14, and creates an ionized paththrough which the main welding current can iiow. Because oi' itshigh-frequency, the high potential imposed on the apparatus will not, byitself, cause more than a slight tingling sensation if contact isaccidently made with it by a person.

Since the high-potential current seeks the path of least resistance tothe ground and will jump an air gap up to 11e in., for example, it isimportant that all parts which are at the high potential, or to. whichthe high-potential may jump, loe well insulated from the ground. Theinsula- .tion used in standard Welding heads is not sumcient towithstand such high voltage. so special precautions are provided. If thestarting uralt is used in conjunction with the head and carriageassembly, shown by Patent m'li, the meinst ing bracket, should. bemounted on on insulating losse not directly on the carriage. Thecomplete assembly above the mounting bracket, except switch por: S canthen he considered to he at the high potential. l the head H is mountedou e, special support, a heavy insulating piece should be insertedbetween the support and the welding head assembly. Generally theinsulation is ii sorted between the support and the mounting bracket orthe arm and hinge, if only latter is used. The rod reel, ii mountedseparately, must also be insulated. The control cable head conu nectorshould always be attached 'to a grounded part of the equipment.

In addition to insulating the welding equipment, it is also necessary toprevent the highirequency current from flowing to the ground through thehead connector control leads, plugs, and control box. Although the twowelding= voltage leads 2S, 28 arethe only ones connected directly acrossthe high-potential source, the radio frequency current will induce othercurrents in adjacent leads. Since this Knight serious-a ly affect thecontrol unit, it is necessary to filter out the high frequency from allthe leads from the head without affecting the Gil-cycle or directwelding current which normally ilows through them. Since the resistanceto flow of an alternating current through an incluctance varies directlywith the frequency, and the resistance to ilow through a capacitancevaries inversely with the frequency, the small choke coils are eachlplaced in series with each lead from the head.

This allows the Sil-cycle or direct current to pass through but resiststhe high-frequency. The choke coils are all contained in the llter unitB. Any small high-frequency currents which pass through the choke coilsare 'by-passed to the ground through the condensers which are con nectedto ground lead 3U.

The control unit A is so designed that it can easily be placed in serieswith the voltage control leads by removing a plug from its normalconnection to the voltage control 24, and inserting it in the 8-polereceptacle contained in the 6 timing unit A. An 8-conductor cable and8-pole plug supplied with the unit A are then connected to a receptaclein the voltage control 24.

When direct current is used for welding, the polarity of the Weldingvoltage leads to the control unit 24 must be correct or the control unitwill not supply current to the rod feed motor I6. Since either straightor reverse polarity may be used for welding, the polarity-reversingswitch 4u is provided on the starting control A. The control case shouldbe well grounded; preferably by means of a separate Wire from the box toa water pipe or the steel building structure.

The timing and control unit A serves to control, automatically, theoperation of the high-frequency starter C and the rate of rod feed atthe start of the weld. The starting relay 82 which has two normallyclosed contacts 8|), I i8 and one normally open contact |48, controlsthe actual starting. Resistance |20 in the armature circuit |22 reducesthe speed of the rod feed motor it during starting. The normally opentime-delay relay |06 prevents the apparatus from welding for a presetperiod of time and is similar to the time-delay relay tot except thatthe latter is normally closed, the tiene of welding. As pointed outalcove relay Il@ is provided with a singlemole, clouhletl'irow G@ whichcloses at applied voltage oi about te volts and opens when the voitdrop-s celcw Gil volts. lt is connected so as to lie :naive to thewelding voltage and controls ci ation ci relay 82 and the two timerslll. Switch oulel he closed when weldi i with A. C.; and ned, placingthe resistance es with i clay coil fili, when welding Switches l and.ilil are provided to actively disconnect time-delay relays 5t andrespectively, from the circuit.

The operation or the control can be understood by assuming the need tomake intermittent fusion welds 1 inches in length and 5 inches apart at24 inches per minute, i-or example. A ll-in. seam weld at 2e inches perminute will take 10 seconds, so the welding time-delay switch 54 is setat the lll-second limit. The space between welds is 6 inches, or 15seconds at 24 inches per minute; therefore, non-welding time-delay relayim? is set at the ieseconcl limit.

The welding carriage supporting the welding equipment is then positionedso that the rod lil is at a point 6 inches away from where the firstintermittent weld is to he made and the contac= tor and travel switchesiitl. l2@ are closed. The opcu=oircuit across the welding voltage leads'il, il@ huma ately causes contact 66 of relay 5E] close, connecting thesupply circuit 84 to tirneedelay relay 06 which starts operating. Duringthis period) contact 552 of tlmedelay relay Mi is open, preventing therod I0 from feeding.

At the end of 15 seconds contact H0 oi' timeu delay relay |08 closes andconnects the supply circuit 84 to relay 82. Relay 82 then operates and:(l) Contact opens the power supply circuit to the travel carriage motorH6 and timeedelay relay E4, contact 52 of which returns to its normallyclosed position and starts the rod feed motor lli; i2) contact il@ cutsresistance |20 into the er mature circuit i222 to reduce the rod feedrate; (3) Contact |43 starts the high-frequency generating unit C. f

As soon as the welding action begins. the opencircuit voltage in circuit64, |80 drops to the normal welding voltage, causing relay 50 to open ycut out the high-frequency starter C, eliminate the eilfect ofresistance l2 from the armature circuit i22, and start the carriagetravel motor it and time-delay relay 54. Relay 50 also disconnectstime-delay relay lilso that it returns to its starting position. Afterthe welding operation has proceeded for seconds, time-delay relaycontact 52 opens and disconnects the weldingvoltage circuit 28, 98,which stops the' rod feed motor it. As the end of the rod i@ burns o,the welding voltage increases until the open-circuit value is reached,and the complete cycle is then automatically repeated.

it should bel noted that during the welding oi`f" time of the cycle thewelding head is at opencircuit potential. Resistance i2@ should beadjusted so that the rod feed on starting is as fast as possible withoutcausing the rod it to stick. if the rod freezes occasionally, moreresistance should be added to the circuit.

There are a number of cases where one or both of the time-delay devices5G, it are not required. When making plug welds, for example, time-delayrelay itt is not needed. This relay can be efectively shunted from thecircuit by closing switch 2G63. The starter d2 will then function assoon as the contacter switch it@ is manually closed, and the weldingwill continue automatically until contact o2 of welding time-delay relay56 opens. The cycle will be repeated immediately, unless the contactorswitch itt is manually opened. When it is desired to provide a delaybefore welding, but no limit on the time of welding, switch illl isopened and switch l2 is moved into circuit relation with circuit l0.With this arrangement, the timer bt is adjusted to a delay of less thanone second so that its contact 52 opens immediately after relay 5toperates and thus prevents the rod lil from feeding until timer H06closesl and starts the welding operation.

In cases that do not require highly accurate timing devices, the weldingperiod may be controlled by a mechanical trip switch operating on a cammechanism by virtue of the relative travel of the head H and work 22. Asingle-pole, singlethrow trip switch 206, for example, may be placed inseries with the welding-voltage lead 26 or ground lead 28. By closingand opening the welding-voltage circuit 26, 28, the trip switch thuscontrols the operation of voltage-relay and the voltage control 24 inthe same way as previously described for the time-delay relays 54, andm6.

The invention is especially suitable for automatic yproduction welding,and intermittent welding, as well as plug welding.

What is claimed is:

1. In an electric fusion welding system comprising a welding-voltageresponsive circuit for controlling the welding rod feed in the weldingcircuit so that the Welding voltage is kept substantially constantduring welding, an automatic high-frequency starting and timing controlcombination comprising a voltage-responsive relay operatively associatedwith said welding circuit so that such relay is responsive to theopencircuit and normal welding voltage differential, a starting relayand a pair of time-delay relays responsive to the operationof saidvoltage-responsive relay and operatively associated with each other sothat one of said time-delay relays is operative as a non-welding timerwhen open welding-circuit voltage is applied to said voltageresponsiverelay, and the other time-delay relay is operative as a welding timerwhen normal welding voltage is applied to the starting relay, said lilWelding time-delay relay having an output circuit operatively associatedwith said weldingvoltage responsivecircuit; said starting relay beingresponsive to the operation of said nonwelding time-delay relay at theend of each nonwelding interval for deenergizing said welding time-delayrelay and causing the rod feed to start at slow speed, a high-frequencygenerator responsive to the operation of said starting relay, the outputcircuit of said generator being coupled to the welding circuit so thatthe high-frequency output starts the welding current now before thewelding rod touches the work, causing normal welding voltage to beapplied to said voltageresponsive relay, deenergizing said non-weldingtime-delay relay and said starting relay, thereby deenergizing saidhigh-frequency generator, and energizing said welding time-delay relayto start the welding period which continues until the welding time-delayrelay stops, opening the weldlng-voltage responsive circuit, which stopsthe rod feed.

2. In an automatic electric fusion welding system, the combinationcomprising a high-irequency generator, means for slowly feeding onewelding electrode toward another welding elec trede, means for applyingthe high-frequency output of said generator to said electrodes, meansfor energizing said high-frequency generator while said electrode isbeing slowly fed by said electrode-feed means, means for supplying saidelectrodes with a Welding current before said electrodes meet by virtueof the action of such high-frequency output in the medium between saidelectrodes, and means responsive to the flow of such welding current,for deenergizing said high-frequency generator and increasing theelectrode-feed rate of said electrode-feed means.

3. In an automatic relay system, the combination comprising avoltage-responsive relay having a contact which closes when the voltageapplied to the input circuit of the relay reaches a maximum value, andopens when such voltage drops below a minimum value, a pair of timedelayrelays operatively associated with said contact, one of said time-delayrelays having a normally open contact and the other a normally closedcontact, a fourth relay having an input circuit controlled by saidnormally open contact, said fourth relay having three contacts, one ofsaid three contacts being normally closed and in the input circuit ofthe normally closed-contact time-delay relay, another contact of saidthree' contacts also being normally closed, and the remaining contact ofsaid three contacts being normally open.

4. In a submerged-melt electric fusion welding system, the combinationwith a welding head including means comprising a rod feed motor forfeeding a metal welding rod toward the work, an automatic voltagecontrol for regulating the speed of said motor so as to keep the weldingvoltage substantially constant, and a high-frequency generator forstarting the welding action before the rod`v touches the work under ablanketof granulated material which when cold is a non-conductor of thewelding current, of a high-frequency starting and timing controloperatively associated with the system for energizing said generatoronly at the start of each weld, comprising a relay having an outputcircuit controlling the operation of said generator, and circuit meansresponsive to the voltage between said rod and the work for operatingsaid relay so that prior to the start of each weld as the rod approachesthe work, the

9 open-circuit voltage o! the welding circuit results in the, operationof said generator the highfrequency output of which is applied to therod and work so as to pass through such granulated material until thewelding current starts to flow, causing the resulting welding voltage toatleet said circuit means and relay so as to deenerglze saidhigh-frequency generator as soon as the welding action starts, saidrelay also having an output circuit operatively associated with saidvoltage control so that the rate oi' the rod feed is reduced when saidhigh-frequency generator is operating.

5. In an electric 'fusion welding system, the combination comprising awelding head, an automatic voltage control. a high-frequency generatorhaving an output circuit coupled to the welding circuit for starting thewelding action, a highfrequency starting and timing control forrestricting the operation of said high-frequency generator to a shortinterval prior to the start of each weld, and means for preventingdamage to the system due to the high-,frequency output of saidgenerator, comprising a high-frequency filter unit located in the'circuits between the welding head and the high-frequency starting andtiming control, each circuit containing-a high-frequency choke-coil, anda grounded highfrequency by-pass condenser.

6. An automatic starting and timing control apparatus for an electricfusion welding system in which a metal welding electrode is fed towardthe work by means including an automatic voltage control circuit, saidapparatus comprising a voltage relay responsive to the open-circuitvoltage of the welding circuit, a non-welding time-delay relaycontrolled by said voltage relay, a starting relay controlled by saidnon-welding time-delay relay. and a welding time-delay relay controlledby said starting relay, said welding time-delay relay controlling theoutput of said automatic voltage control circuit so as to stop theelectrode feed at the end of each weld, whereby the end ing circuitmeans electrically connecting said.

electrode to a source of welding current, and means having an inputcircuit responsive to the welding voltage for energizing said rodfeeding means to keep such voltage substantially constant, of means forautomatically starting the welding action of such machine at apredetermined point in the path of travel of said carriage means,comprising mean acting to render said input circuit effective at suchpoint, and relay means responsive to the open-circuit voltage of thewelding circuit acting to deenergize the carriagev driving means untilkthe welding action starts, and means operative only while said carriagemeans is stationary for starting the welding action, said relay meansbeing operative in response to the normal welding voltage to againenergize said carriage driving means.

8. An automatic electric fusion welding process involving high-frequencystarting and automatic timing, which is especially suitable for plugwelding, intermittent welding, and production line welding, whichcomprises generating and applying a high-frequency potential between thework and a welding electrode connected to a welding current source whileslowly feeding such electrode toward the work, automaticallydiscontinuing the generation of such high-frequency potential andstarting relative traverse motion between the electrode and work as soonas the welding voltage drops when the welding operation starts, carryingout such welding operation for a desired period of time, stopping thewelding operation without discontinuing the relative traverse motionbetween the electrode and work for a desired interval. and automaticallyrepeating the cycle beginning with the high-frequency potential f.generation.

oi the electrode melts and the resulting opencircuit voltage operatessaid voltage relay which energizes said non-welding time-delay relay. sothat the latter operates said starting relay at the end o! eachnon-welding period, which in turn causes the welding time-delay relay toreturn the rod feeding function to said voltage control circuit, saidstarting relay being provided with means associated with said voltagecontrol circuit for restricting the rate at which the rod is fed towardthe work immediately prior to the starting of the welding action, andsaid starting relay also being provided with means for controlling theionization oi' the medium between the electrode and the work so that thewelding action lstarts before the electrode actually touches the work.

'1. The. combination with a submerged-melt electric seam welding machineincluding carriage means supporting a welding electrode for movementalong the scena-means ior driving said carriage means, means ior feedingsaid electrode starts.

JOHN A. KRA'IZ. HENRY G. THOMA.

n REFERENCES CITED The following references are of record in the illeoi' this patent:

UNITED STATES PATENTS Number Name Date 1,146,926 conrad J y io, 191s1,701,372 Jefes b.-.4, 1929 2,152,785 Blaukenhuehler Apr. 4, 19392,340,093 White Jans-25, 1944 2,365,612 White Dec. 19, 1944

